rez tools visibility behavior not backwards compatible from 2.61.0

[maxnbk]

between 2.60.1 and 2.61.0 , src/rez/system.py changed it's determination of "whether to pass rez-tools along to the environment or not" from being a "is it which-able, to, "is the currently importable rez module also a production install".

This does not have to be the case, and makes sense not to be the case. In our production environment, we have a production install of rez tools exposed on the PATH, and a separate version of rez exposed as a module (via a package), and the module is not a production install, while the one on the PATH is.

When migrating our rez-tools versions to newer versions of rez, nothing changes, but when we migrate the package-version of rez to newer versions to 2.60.0+ , the module version of rez, when performing a solve, no longer exposes the rez tools from the PATH to the downstream resolved context.

This occurred here, although subsequent edits occur to expand the logic to lib64, etc. https://github.com/nerdvegas/rez/compare/2.60.1...2.61.0 "-update to system.rez_bin_path that is more reliable" (in ./src/rez/system.py)

Environment

• CentOS-7.6
• Encountered when migrating components from rez-2.52 to 2.100+
• rez-python-2.7

To Reproduce

1. Expose rez tools via PATH
2. rez-env to an environment with a rez rez-package
3. Use that rez-package's api to create a ResolvedContext and execute the shell
4. After executing the shell, inspect the PATH and find that the rez-tools are no longer available.

More direct reproduction sample that can be bash-executed, provided you have a python-2 package, and the rez package-versions you want to inspect the reproduction for (Pardon the backslash hell, I wanted a oneliner):

[maxnbk@comp rez]$ REZ_KEEP_TMPDIRS=1 rez-env python-2 rez-2.109.0 -- bash -c "echo \$PATH; echo \$PYTHONPATH; python -c 'import rez; print(rez.__file__); from rez.resolved_context import ResolvedContext; rc = ResolvedContext(package_requests=[]); command=[\"/usr/bin/echo\", \"\\\$PATH\"]; from rez.system import System; print(System().rez_bin_path); rc.execute_shell(command=command)' "
/home/maxnbk/packages/python/2.7.18/_v/a/bin:/usr/local/bin:/usr/bin:/bin:/home/maxnbk/rez/bin/rez
/home/maxnbk/packages/rez/2.109.0/platform-linux/arch-x86_64/os-rocky-8.5/python-2.7
/home/maxnbk/packages/rez/2.109.0/platform-linux/arch-x86_64/os-rocky-8.5/python-2.7/rez/__init__.pyc
None
/usr/local/bin:/usr/bin:/bin # This line should look like the last line in this codeblock
[...]
[maxnbk@comp rez]$ REZ_KEEP_TMPDIRS=1 rez-env python-2 rez-2.60.1 -- bash -c "echo \$PATH; echo \$PYTHONPATH; python -c 'import rez; print(rez.__file__); from rez.resolved_context import ResolvedContext; rc = ResolvedContext(package_reque
sts=[]); command=[\"/usr/bin/echo\", \"\\\$PATH\"]; from rez.system import System; print(System().rez_bin_path); rc.execute_shell(command=command)' "
/home/maxnbk/packages/python/2.7.18/_v/a/bin:/usr/local/bin:/usr/bin:/bin:/home/maxnbk/rez/bin/rez
/home/maxnbk/packages/rez/2.60.1/platform-linux/arch-x86_64/os-rocky-8.5/python-2.7
/home/maxnbk/packages/rez/2.60.1/platform-linux/arch-x86_64/os-rocky-8.5/python-2.7/rez/__init__.pyc
/home/maxnbk/rez/bin/rez
/usr/local/bin:/usr/bin:/bin:/home/maxnbk/rez/bin/rez

Expected behavior I expect the rez-tools to still be available after the execution of the RC's shell.

Actual behavior They aren't.

Regression Bug did not occur in 2.60.1, although we were working from 2.52.1

[maxnbk]

Updated the reproduction information with a helpful oneliner to reproduce in bash, provided you have desired package-versions installed and/or tweak the resolve request according to what you have available.

[nerdvegas]

Yeah I think this regression is a pure logic fail! I figure we just didn't take into account the case where rez-as-rez-pkg should keep a separate production install of rez visible.